The present invention is directed to a method and measurement system for the control of an active charge surface in the under-pressure gas carburizing process, advantageously in the atmosphere of a ternary carburizing mixture, one which includes ethylene, acetylene and hydrogen.
From Japanese Patent Publication No. JP 2002173759 a control system of a gaseous atmosphere and a device which co-works with it for vacuum carburizing is known. In this system the carbon potential (PC) of the atmosphere created on the base of hydrocarbons is measured and regulated by a calculation system on the basis of signals from the pressure process sensors and the partial pressure of a hydrogen sensor in the process chamber or outlet pipes.
From German Patent Publication No. DE 10359554 one knows the set for the details carburizing in the vacuum furnace, a set which is able to suit the carbon supply to the actual details' demands. In the set, in the working furnace chamber or on the outlet pipes in front of the vacuum pump, the sensors have been installed, the sensors of hydrogen concentration and/or acetylene and/or combined carbon content, e.g. mass spectrometer, sensors of which signals, after the processing in the calculating system, is transferred an impulse to the metering valve of the demanded proportioning size of e.g. acetylene, appropriately to the temporary demand of the charge depended on the actual carbon content in steel.
Another solution was presented in U.S. Pat. No. 6,846,366, where one finds the description of a device and carburizing method with pressure from 13 to 1000 Pa, in an atmosphere containing less than 20% capacity of carbon monoxide, of whose content is controlled by the heat conduction measurement with a Pirani vacuum meter in order to regulate the temperature, pressure and gaseous atmosphere process parameters.
From Polish Patent Publ. No. P-356754 one knows the ternary mixture containing ethylene, acetylene and hydrogen or ammonia, a mixture which during the carburizing process in the underpressure proves the synergetic effect of a high degree of hydrocarbons on the charge surface. This results in skilful carbon transmission from the mixture to the charge surface without the creation of burdensome by-products in the form of tar or/and soot. In the process the carbon transfer from the atmosphere to the charge area takes place by the indirect phase, which is created on the whole charge area—hydrogenated carbon deposit (Kula et al 2006). Carbon transmission to the surface occurs to be highly intensive, and on these grounds the technological process is divided into short, several minutes' carbon boost phase, and the phase of entirely diffusive carbon distribution into steel. These are the non-stationary and non-equilibrium process conditions, of which the effect course and diffusive layer growing may be programmed entirely on the basis of a computer simulation through the expert system, including the data base on treated materials and physical and mathematical process model. In the conditions of a changeable productive line the expert system programs the process course in a correct way provided that one introduces in it the required layer parameters, process temperature, steel grade and active charge surface, one which is difficult to estimate in the production conditions which may result in some error.